Heredity 75 (1995) 425—433 Received 20Apr11 1995 Mapping of QTLs for glandular trichome densities and Trialeurodes vaporariorum (greenhouse whitefly) resistance in an F2 from Lycopersicon esculentum x Lycopersicon hirsutum f. glabratum CHRIS MALIEPAARD*, NOORTJE BAS, SJAAK VAN HEUSDEN, JOOST KOS, GERARD PET, RUUD VERKERK, RIA VRIELINK, PIM ZABELj- & PIM LINDHOUT DL 0-Centre for P/ant Breeding and Reproduction Research (CPRO-DLO), P0 Box 16, 6700 AA Wageningen, Department of Molecular Biology, Wageningen Agricultural University, Dreijenlean 3, 6703 HA Wageningen and Department of Plant Breeding, Wageningen Agricultural University, P0 Box 386, 6700 AJ Wageningen, The Netherlands AnF2 of an interspecific cross between cultivated tomato (Lycopersicon esculentum cv. Money- maker) and L. hirsutum f. glabratum was used to generate an RFLP linkage map. Distortion of single locus segregation (1:2:1) was observed for a number of markers from different chromo- somes, always with a prevalence for L. hirsutum f. glabratum alleles. To identify quantitative trait loci (QTL5) for greenhouse whitefly (Trialeurodes vaporariorum) resistance in this F2 population, life history components of the greenhouse whitefly population were evaluated. Two OTLs affecting oviposition rate mapped to chromosome 1 (Tv-i) and 12 (Tv-2). F3 lines homozygous for either the L. esculentum allele or the L. hirsutum f. glabratum allele at one or both loci confirmed the effects of Tv-i and Tv-2. The F2 population was also evaluated for segregation of type IV and type VI glandular trichome densities. Two QTLs affecting trichome type IV density (TriIV-i and TriIV-2) and one affecting type VI trichome density (TriJ/I-i) mapped to chromosomes 5, 9 and 1, respectively. These results do not support the hypothesis that the density of type IV trichomes is involved in whitefly resistance. Keywords:insectresistance, Lycopersicon esculentum, L. hirsutum f. glabratum, Trialeurodes vaporariorum, QTL mapping, segregation distortion. A high level of resistance has been found in the Introduction wild species L. hirsutum f. glabratum (De Ponti et a!., Thegreenhouse whitefly (Trialeurodes vaporariorum 1975; Bas et at., 1992) and L. pennellii (Gentile et a!., Westw.) is an endemic pest in greenhouse tomato 1968). Tests for resistance using clip-on cages (Lycopersicon esculentum) cultivation in northern (Berlinger & De Ponti, 1981; Romanow et a!., 1991) Europe. As all tomato cultivars are susceptible have revealed large differences between L. hirsutum (Gentile et al., 1968; De Ponti et a!., 1975) and f. glabratum and L. esculentum with respect to the because considerable costs are involved in control- life history components oviposition rate (OR), adult ling the pest chemically or biologically, there is an survival (AS) and preadult survival (PS) (Bas et al., urgent need for resistant cultivars. Unfortunately, 1992). breeding for whitefly resistance is hampered by the An association between insect resistance and the apparent quantitative inheritance of the resistance, presence and density of type IV and type VI glandu- the variation in the whitefly population and large lar trichomes in L. hirsutum f. glabratum and L. environmental variation of population growth (De pennellii has been reported by several authors Ponti et a!., 1975; Bas et a!., 1992). Hence, large (Snyder & Carter, 1984; Fery & Kennedy, 1987; plant populations are required for resistance tests. Goffreda et at., 1988, 1990a,b; Weston et a!., 1989). Trichome type IV is present in L. pennellii and L. *Correspondence hirsutum f. glabratum but absent in L. esculentum. C 1995 The Genetical Society of Great Britain. 425 426 C. MALIEPAARD ETAL. Trichome type VI is present in all Lycopersicon major QTLs affecting whitefly oviposition rate and species (Luckwill, 1943) but more abundant in L. three genomic regions associated with trichome den- hirsutum f. glabratum than in L. esculentum (Fery & sities. Marker-aided selection of F3 lines confirmed Kennedy, 1987). In F2 progenies from L. esculen- the presence of the QTLs for whitefly oviposition turn x L. hirsutum f. hirsutum an association was rate. observed between resistance to the two-spotted spider mite (Tetranychus urticae Koch) and type IV and type VI trichome densities (Carter & Snyder, MateraIs and methods 1985). Also the exudates from glandular trichomes of wild tomato species may be involved in insect P/ant material resistance. Goffreda et al. (1988) reported that A cross was made between L. esculentum cv. Money- glucose esters in the exudate of type IV trichomes in maker and L. hirsutum £ glabratum using one plant L. pennellii were involved in mediating resistance to of Moneymaker as the pistil parent and one plant of the potato aphid (Macrosiphum euphorbiae Thomas). a resistant accession of L. hirsuturn f. glabratum Williams et al. (1980) showed that 2-tridecanone in (CGN1.1561) as the pollen parent. This accession is type VI trichome glands of L. hirsutum f. glabratum maintained by selfing at the Centre of Genetic had an insecticide activity to Manduca sexta L., Resources (part of CPRO-DLO). The F1 was selfed Heliothis zea (Boddie) and Aphis go&sypii Glover. and an F2 population of 288 plants was obtained Moreover, 2-tridecanone is far more abundant in L. from two F1 plants. All F2 plants were selfed by hirsutum f. glabratum than in L. esculentum (Wil- hand-pollination to generate F3 seeds. liams et al., 1980; Zamir et al., 1984). Fery & Ken- nedy (1983, 1987) observed significant effects of both type VI trichome density and 2-tridecanone Greenhousewhite fly concentration on resistance to Manduca sexta in seg- Astock culture of whiteflies was reared on suscep- regating progenies from L. esculentum x L. hirsutum tible 'Moneymaker' plants. Tomato plants were inoc- f. glabratum but no association was found between ulated as described by Bas et a!. (1992) and life these two characters. history components of the greenhouse whitefly were The genetics of these characters related to insect calculated per cage according to Van Giessen et a!. resistance appears to be complex. For example, (1995): Zamir et al. (1984) reported association of the level of 2-tridecanone in L. hirsutum f. glabratum with five oviposition rate(OR) =2e/{d(m+n)} day, marker loci on at least four different chromosomes. adult survival (AS) =(m/n)'day, Nienhuis et a!. (1987) found association of 2-trideca- preadult survival(PS) =p/e, none level with marker loci on three linkage groups where e =numberof eggs, d number of days and of type VI trichome density with one of these (=3)between redistribution and removal of the marker loci. Lemke & Mutschler (1984) suggested adult whiteflies, in= numberof surviving adults that the presence of type IV trichomes in L. pennellii after 3 days, n =numberof adults used for inocula- is controlled by two dominant unlinked genes tion (=5)and p =numberof pupae after 5 weeks. whereas type IV trichome density is conditioned by If there were fewer than five eggs or if the leaves more than two genes. deteriorated before the flies emerged, the estimate Despite these studies, the mechanism and inherit- for PS was excluded from the analysis. If more than ance of whitefly resistance still remains obscure. half of the inoculated whiteflies died, OR could not Nowadays, inheritance of quantitative traits is suc- be determined accurately and, as a consequence, cessfully investigated by using molecular markers they were excluded. To produce a normally distrib- such as restriction fragment length polymorphisms uted error term, an arcsin transformation was used (RFLPs). Quantitative trait loci (QTLs) for insect- for AS and PS. resistance-related characters have been identified in several crops like tomato (Nienhuis et a!., 1987), potato (Bonierbale et a!., 1992, 1994) and maize Cllp-oncage tests (SchÔn et al., 1993). Intwo neighbouring greenhouse compartments at To map QTLs involved in whitefly resistance and 20/15°C, 12 L. esculentum cv. Moneymaker, 12 L. trichome densities, we have used a set of RFLP hirsutum f. glabratum, 12 F1 and 288 F2 plants were markers with known map positions (Tanksley et a!., grown. Plants were pruned regularly and were low- 1992). Here we present the identification of two ered so as to keep the height at 2 m above the soil. The Genetical Society of Great Britain, Heredüy, 75, 425—433. QTLS FOR WHITEFLY RESISTANCE 427 Each compartment contained six rows of 27 plants one or two plants of each of the F3 lines in every each: one plant of each of the parents, one F1 and row. The plants were randomized within a row. One 24 F2 plants. One block consisted of two rows. In the block consisted of two rows. Plant cultivation and analysis individual plant observations for OR, AS the determination of the whitefly life history compo- and PS were corrected for block effects. The block nents were the same as in the F2 clip-on cage test. effect was calculated as the difference between the block mean of the 48 F2 plants in a block and the overall mean of the F2. Considering the large num- F3compartment test ber of F2 plants in each block (48) we assumed that TenF3 lines and controls (parents and F1) were differences between blocks resulted from environ- grown separately in isolated greenhouse compart- mental rather than genetic factors. ments under commercial tomato production condi- Fourteen weeks after sowing, whiteflies were col- tions at 20/15°C. Each compartment consisted of 20 lected at random from a stock culture. For adapta- plants. Fifteen female whiteflies were released near tion, whitefly females were released in clip-on cages the bases of every plant. After 94 days, empty pupae attached to each plant. After 4 days, flies were col- present on the three top leaflets of each leaf were lected from each plant and 20 survivals were evenly counted. redistributed in four clip-on cages attached to the To adjust for differences in leaf architecture, the abaxial side of two young leaves of the same plant.